VENUSIAN FISHER LEARNS ABOUT MARS

This article was published in the March 1, 2025 Edition. 

Death Valley National Park is the hottest, lowest, and driest place in North America, captivating visitors with its unique geological features striking temperature contrasts between its searing valley floor and the snow-capped peaks. 

This stark landscape, shaped by dramatic flash floods, tectonic plates and fierce winds, showcases the remarkable resilience of life that thrives against all odds. It is otherworldly. 

So otherworldly, in fact, that it serves as the backdrop for astronomers’ discussions about the cosmos. Last weekend, the park hosted the Death Valley Dark Sky Festival, an annual celebration of its pristine night skies and their significance in planetary science. 

The desert environment is one of the best analogs for studying extraterrestrial landscapes, allowing astronomers to draw conclusions about dry regions beyond our planet. This scientific cross-comparison is known as comparative planetology, as NASA geomorphologist Dr. Serina Diniega explained during her talk, “Wind and Frost in Another Very Dry Place – Mars! 

Mars, even to the casual observer, bears a striking resemblance to Death Valley in satellite imagery, featuring sand dunes, salt flats, and playas. Like Death Valley, the Martian surface is actively reshaped by wind, seasonal frost, and gravity. 

For instance, sand dunes on Mars form and evolve much like those on Earth. Wind moves granular material over time, allowing grains to interact with each other and the ground, ultimately accumulating into larger structures. Understanding the behavior of sand dunes in places like Death Valley helps scientists make sense of Martian geological phenomena, such as gullies 

Gullies are trenches in the dunes with apron-like features at the top and bottom. On Earth, they often form from displaced water flow and are visible throughout Death Valley, including in Ubehebe Crater, which resulted from a powerful volcanic steam explosion. 

The Newton Crater on Mars, a large basin formed by an asteroid impact, closely resembles Ubehebe Crater, complete with narrow gullies carved into its northern wall. The discovery of gullies on Mars excited astronomers because proving they formed similarly to those on Earth – with water – could provide hard evidence that Mars was once a wetter planet. 

And if Mars was once wet, it might have had life on it. 

But Diniega also sees these gullies on sand dunes, and with more data, she’s seen new gullies forming on sand dunes, despite the fact that there’s hardly any accessible water in the planet’s atmosphere. So, the initial explanation didn’t track in her research of present day activity. 

That’s the tricky thing about comparative planetology: you only get a snapshot of the extraterrestrial, and you have to find a way to explain the entire landscape formation. In reality, these places can form unbelievably different from Earth’s processes, even if the landforms look the same. 

“Think about it as a big puzzle; we’re trying to really decode things,” she said. “This is very complicated because many processes happen on landscapes. Some of these are very short time scales and some of them over very long time scales. Some of them act continuously and some of them act very suddenly.” 

That was the case for the gullies. The results on Earth and Mars looked similar, but the chemical make-up of Mars complicates the story. While it’s not impossible that Mars gullies formed in the past with water, that’s almost certainly not what’s happening right now. 

Almost all of the current frost on Mars is dry ice, which behaves very differently from water ice. 

You might be familiar with dry ice from science class or a fun cocktail (depending on where you tend to pay attention.) It’s a funky-looking substance because it turns directly into a gas when it warms, rather than water ice which melts to liquid. Dry ice also has a significantly lower freezing point than water, with dry ice freezing at approximately -109.3°F compared to water’s freezing point of 32°F. 

Diniega’s team ultimately suggested that these gullies result from the movement of dry ice, not water ice. They presume it mimics fluid dynamics when it warms, leading to the erosion and reshaping of Martian surface features without the involvement of water. 

This also helps to explain a specific kind of gully formation seen on Mars dunes, characterized by relatively constant width and by raised banks along the sides and without an apron closure, what you’d imagine seeing if a boulder rolled down a hill. 

Except instead of boulders, pits punctuate these trenches. The phenomenon has puzzled astronomers since they first saw them. 

That is, until Diniega’s team discovered – on a sand dune in Utah – that dry ice floats down sand dunes like hockey pucks, while blocks of water ice and wooden blocks slide only incrementally on sand before stopping. 

This is because of the gas dry ice emits while warming, which essentially allows it to “hoverboard” down the slope. The longest known gullies of this type extend almost 1.2 miles down the side of a large sand dune inside Russell Crater on Mars. 

Mars’ dry ice anomalies don’t stop there; they also include geysers. In 2003, astronomers noticed spider-like geological scars on the Martian surface, which puzzled them until NASA scientists recently modeled a theory in the lab. They found that carbon dioxide gas from dry ice builds up beneath frost until sunlight penetrates the surface in spring, releasing the gas in a pressurized system. 

Now, the prevailing hypothesis suggests these geysers are responsible for the surface scars. At Mars’ frosty poles, dry ice behaves much like water snow on Earth, resulting in clouds of debris during springtime. Meanwhile, the southern polar cap features a “swiss cheese” terrain, with pits that widen over time due to the interplay of dry and water ice. 

Astronomers are still trying to figure out exactly what this means for Mars’ atmosphere – whether that carbon dioxide stays in the atmosphere, goes back into space, or does something else entirely. 

As researchers like Dr. Serina Diniega continue to unravel the complexities of these environments, we gain deeper insights into the history of Mars and the possibility of past life there. 

Studying such extremes on Earth not only informs our exploration of other worlds but also deepens our appreciation for the intricate dynamics that shape our own planet. As we look to the stars, places like Death Valley remind us that the mysteries of the universe are often reflected in the landscapes right beneath our feet.